Well I did this some time ago, I still think writing things done may help if I encounter this again.
To move the mail server to another server, and lost mails as less as possible, here is my steps:
- Set your DNS server so your domains get a lower TTL. Do this as early as possible […]

Well I’m using spambayes to do spam filter work, and it does do its work well: It will only move the mails it’s sure are spams to the spam folder, and the mails it’s sure are not spam to the non-spam folder. And something in between to the unsure folder.
For me […]

# ALLOW UNDERSCORE IN EMAIL DOMAIN NAME # domains shouldn’t use the underscore character “_” but some # may. Because John Postel, one of the architects of the Internet, # said “Be liberal in what you accept and conservative in what you # transmit, we choose to allow underscore in email domain names so […]

Here is the how to
Install the /usr/ports/mail/p5-Mail-SpamAssassin and /usr/ports/mail/spamass-rules port
Put these in /etc/rc.conf
spamd_enable="YES"
spamd_flags="-d -m 1 -r ${spamd_pidfile}"
The “-m 1″ said only folkone spamd instance. I don’t have too much trafic so one instance is OK.
copy my local.cf to /usr/local/etc/mail/spamassassin and restart spamd to check the rules out.
There are two choices for using spamassassin with exim: […]

Everything is backuped when I got up in the morning. So packed the PC and 80G and went to repair it.
FT enough, after I got to the shop, everything is fine in the first try. Don’t know what to say. Maybe the HD and PC just want to travel around
That guy in the […]

According to POST-INSTALL-NOTES:
1 Clear the sendmail queue and stop the sendmail daemon.
As this is a new machine, I just set sendmail_enable to ‘NONE’ and reboot the box
2 Adjust mailer.conf(5) as appropriate.
Here is the new one, with old sendmail settings comment out
# $FreeBSD: src/etc/mail/mailer.conf,v 1.3 2002/04/05 04:25:12 gshapiro Exp $
#
# Execute the "real" sendmail program, named […]